In general, the rewinding or coiling of springs in lawn mowers, chainsaws and similar equipment is done by hand when the spring is being replaced after motor repair. Insertion of the spring onto the spring arbor or spring housing is typically done by hand. Basically, the individual that has done the repairs holds the inner end of the spring with his or her fingers, and then proceeds to wind the concentric spring coils of the ribbon-like spring upon each other as tightly as possible. The spring is prevented from unwinding simply by continually grasping it with the fingers.
Some care obviously has to be exercised while handling a spring in the foregoing fashion to prevent the spring from unwinding. The spring has a tendency to unwind longitudinally or to pop out of place vertically, sometimes with a fair amount of force. Hand-rewinding is hard on the finger muscles, and often can result in pinched fingers and no small amount of frustration, since hand-rewinding calls for manual dexterity and patience. Hand-rewinding is still the most widely used technique for rewinding such starter springs, however, since there is a general lack of an ineffective and cheap instrument to perform the operation mechanically.
A number of hand-operated spring rewinding devices have been known, such as in the watch making art for rewinding of a watch mainspring. U.S. Pat. No. 1,812,494 is one such example. Such spring rewinding devices have a winding element which is received within a housing. The inner end of the spring to be rewound is attached to the winding element with the outer end of the spring being unrestrained and located exteriorly of the housing, along with the remainder of the spring. The winding element is rotated to pull the spring material into the housing for winding about the winding element in rewinding.
Once the spring is rewound, the winding element is removed from the housing, with the rewound spring either removed from the winding element for hand insertion into the motor housing, or charged by some means directly from the rewinder onto the spring arbor.
Some attempts have been made to adapt this watch spring rewinding technology to starter springs. Two such examples are U.S. Pat. Nos. 3,748,716 and 4,183,268. While interesting, such starter spring rewinders do not seem to have met with any significant commercial success, since hand-rewinding still remains the principal way to rewind these starter springs.